Tag: CERN

Let me start this off by first noting this is an unconfirmed report. We don’t have anything solid yet. Keep that in mind, please!

Via my pal Kiki Sanford comes news that the results of an experiment showing neutrinos moving faster than light (FTL) may have been due to equipment malfunction. Science Insider is reporting, citing unconfirmed sources, that a GPS had a bad connection to a computer, and this caused the timing for the experiment to be thrown off:

According to sources familiar with the experiment, the 60 nanoseconds discrepancy appears to come from a bad connection between a fiber optic cable that connects to the GPS receiver used to correct the timing of the neutrinos’ flight and an electronic card in a computer. After tightening the connection and then measuring the time it takes data to travel the length of the fiber, researchers found that the data arrive 60 nanoseconds earlier than assumed. Since this time is subtracted from the overall time of flight, it appears to explain the early arrival of the neutrinos. New data, however, will be needed to confirm this hypothesis.

Here’s some background. A few months ago, scientists in Europe made a startling announcement: they had measured the velocity of neutrinos, a type of subatomic particle, and found they were moving faster than light. They created a packet of neutrinos in one spot, detected them in another, and then very carefully timed how long the flight took. By dividing the distance by the time, they found that the neutrinos got from Point A to Point B 60 nanoseconds faster than light would!

Obviously, this caused quite the uproar. The scientists involved were careful to state they were’t actually claiming FTL travel, just that they got this result. They also asked for help in figuring it out. Lots of ideas were aired out, and new experiments tried, but in the end timing was always the critical factor. The distance the particles traveled was known to very high accuracy, but the timing was far more difficult to ascertain.

The timing was done using a GPS system, which in theory is accurate enough to do the trick. There are lots of ways you have to be very careful when using GPS, and a lot of folks focused on that. Most of these were pretty high level issues (accounting for relativity, for example), but I never heard anything like "Hey, better try reconnecting that there cable."

To be clear: this is unconfirmed, and still in the rumor stage. If this turns out to be the case, though, then we’re essentially done here. I’ll be very curious to see how this plays out over the next few hours and days. Stay tuned!

Today, scientists at CERN in Geneva announced their results for their search for the Higgs boson, a subatomic particle that, if it exists, is thought to be responsible for giving other particles mass. It’s no exaggeration to call it a keystone in quantum mechanics, and finding it for sure will be a huge accomplishment for particle physicists.

So, did they find it?

Maybe. Then again, maybe not.

Um, what? OK, this’ll take a wee bit of explaining.

Last things first

I said Higgs, Magnum. HIGGS.

First, the conclusion, so at least you have that in mind as you read the rest. There are two experiments running at CERN looking for the Higgs particle. They don’t smash particles together, look around with magnifying glasses and tweezers, and then yell “AHA!” when they find one. Instead, they build up a picture of it after doing gazillions of particle collisions. After a year of runs, both experiments see something that might be Higgs, but they’re not 100% sure. One sees something at about the 94% confidence level, the other at 98%. That’s pretty good, but it’s not enough to be completely sure. It seems likely they’ve found something, but it’s like a fuzzy picture: it looks like Higgs, but it still might be something else.

So why can’t they be sure one way or another?

CSI: Geneva

Basically, what the Large Hadron Collider at CERN does is whip protons around at nearly the speed of light, then smashes them into each other. At that speed they have huge energies, and when they collide that energy gets converted into matter: other particles. Like shrapnel, these new particles explode away from the collision site. Many of these new particles aren’t stable; they decay into yet lower energy particles after incredibly short time intervals. For example, electron and protons are almost certainly stable over long times (like the lifetime of the Universe), but neutrons decay after only a few minutes, turning into a proton, and electron, and a particle called an antineutrino.

So these daughter particles from the proton collisions in LHC decay, and they have daughter particles, and some of those decay, and so on. At the LHC there are two ginormous detectors called ATLAS and CMS. Both of these, in essence, measure the energy of the particles that hit them; like forensics team, they look at the aftermath of the collision and try to work backwards to figure out what happened.

We know to some extent how much energy is expected from these collisions due to all the particles that are currently known, so those can be accounted for. But if there’s some excess of energy, that could very well indicate a new particle. And we have theories as to how much energy the Higgs particle should have. So the energies are measured, calibrated for known particles, and the excesses are examined.

What both experiments found is an excess of energy — a bump in the graph — indicating a particle that has an energy* about 125 times that of a proton — right in the expected range for the Higgs particle. That’s exciting! But what they’re doing is counting up things statistically, so they can’t be 100% sure. The bump in the graph is still fuzzy.

On Friday, a news story came out that a second experiment seems to support the results of an earlier experiment which showed neutrinos might be moving faster than light. I commented about this on Google+ at the time, but I want to post about it here as well. Let me be clear: this new result does not confirm FTL neutrinos! What it did was essentially eliminate one possible source of error. A big one still remains.

Let me recap: In September, a team of scientists at CERN working with the OPERA detector in Italy found that beams of neutrinos — subatomic particles that can travel straight through matter — seemed to get from the source in Geneva to the target in Italy 60 nanoseconds faster than a beam of light would make the trip. If true, it means they were moving faster than light (what scifi geeks like me call FTL) which, according to all the physics we understand, is impossible.

There was a lot of criticism of the experiment, as was expected and as it should be! It fell into two broad categories: a problem with the way they created the neutrinos, and a problem with timing.

The neutrinos were created at the accelerator at CERN as bursts containing gazillions of the particles. They move at essentially the speed of light, which is very fast. In fact, while the duration of the burst of neutrinos was very short in human terms, it was still long enough to blur out the results significantly. It’s like standing by the side of the road and trying to figure out when a cluster of cars passes you; do you measure the front of the cluster, the middle, or the tail end? In the case of the neutrinos, they didn’t know which neutrino was which; they measured all of them in the burst and used a statistical method to get an average travel time for each burst.

This is what a second experiment tried to answer. Using a different method the second time around, they were able to significantly tighten up the burst of neutrinos, reducing the error in the measurement by quite a bit. What they found were results consistent with the first experiment: the neutrinos traveled the 743 km trek 60 nanoseconds faster than light.

Holy cow! Does this prove the result?

No. Don’t forget the second source of error: timing. Most people, including me, think that the way they timed the experiment may be the source of the problem. This second experiment used the same timing techniques as the first! So if that’s the source of the error, this doesn’t really change anything.

And either way, we’re left where we were before: with a weird result that cannot really be confirmed or refuted without an independent experiment done by another group. That’s how science works.

I’ll note that another team of scientists has said the FTL results must be wrong due to energy arguments; that may be correct, but I still want to see a wholly separate experiment done. It’s much like nuking the aliens from orbit: it’s the only way to be sure.

If you haven’t heard about the experiment that apparently showed that subatomic particles called neutrinos might move faster than light (what we in the know call FTL, to make us look cooler), then I assume this is your first time on the internet. If that’s the case, then you can read my writeup on what happened.

Basically, neutrinos move very very fast, almost at the speed of light. Some scientists created neutrinos at CERN in Geneva, and then measured how long it took them to reach a detector called OPERA, located in Italy. When they did the math, it looked like the neutrinos actually got there by traveling a hair faster than the speed of light! 60 nanoseconds faster, to be accurate.

Was relativity doomed?

Nope. In fact, relativity may very well be what saves the day here.

First, most scientists were skeptical. Even the people running the experiment were skeptical, and were basically asking everyone else for help. They figured they might have made a mistake as well, and couldn’t figure out what had happened. Relativity is an extremely well-tested theory, and doesn’t (easily) allow for FTL. Despite some headlines screaming that Einstein might be wrong, most everyone figured the problem lay elsewhere.

Most everyone zeroed in on the timing of the experiment, which has to be extremely accurate. The entire flight time of a neutrino from Switzerland to Italy is only about 2.4 milliseconds, and the measurement accuracy needs to be to only a few nanoseconds — mind you, a nanosecond is a billionth of a second!

The scientists used a very sophisticated GPS setup to determine the timing, so that has been the focus of a lot of scrutiny as well. And a new paper just posted on the Physics Preprint Archive may have the answer… and it uses relativity.

After more than a decade of triumph, setbacks, and much sturm and drang, the Large Hadron Collider made history last night by taking two beams of protons and smashing them head on at just a whisper under the speed of light.

Yay!

The LHC is the world’s largest physics experiment, and is attempting to recreate conditions in the Universe when it was only a fraction of a second old. At that point, pressures and temperatures were so high that the laws of physics were somewhat different than we’re used to. These conditions are extremely difficult to duplicate, which is why it’s taken so long to get the LHC running. The collider uses extremely powerful magnets to guide and accelerate two beams of protons to nearly the speed of light. They go around the collider in opposite directions, then are tweaked to smack into each other. The huge energies of the collision create particles and conditions that can be detected and used to test theories of how the Universe behaves.

There were some minor glitches before the protons could be injected into the main collider last night, but once things got going, the beams were sent at each other at full power. The energies were ramped up to 3 TeV, or three trillion electron volts (a unit of energy).

Now, 3 TeV is not much energy in human terms. It’s roughly the amount of energy of a single mosquito in flight. But for a single proton, 3 TeV is huge, vast, incredible, brobdingnagian, ginormous! When the two proton beams are at full power, they contain the same kinetic energy as a battleship moving at several kph! So we’re talking about powerful events, indeed.

I visited CERN and the LHC a couple of years ago, and wrote up my thoughts. I was of the opinion then, and still am now, that this will be a revolution in physics.

I made a video of that tour, too.

My congratulations to the hordes of people who made this moment possible. It has been a long, difficult journey indeed, but now the real voyage is underway. May the wild physics rumpus begin!

And I love that graphic. 10∞? That’s a big number. You’d think magnifying the Higgs by that amount would make it look bigger.

Anyway, read the whole thing, because it’s pretty funny. Of course, this is a joke, and Ebay will no doubt take it down soon, so look before it’s gone and you’re doomed to travel the Universe forever with your mass kicked.

These images, as beautiful and hi-res as they are, still cannot convey the awesome size and scale of the LHC. It’s been a year and a half since I stood there, 100 meters below of the surface of the Earth, gawking slack-jawed at ATLAS, CMS, and the other magnificent machinery, and it almost seems like a dream to me. But then I shake out of it and remember: this is what we do, and it’s real.

Secrets of the Universe? We humans figure that stuff out over coffee. What’s next?

After a series of setbacks — some devastating, holding up the world’s largest scientific experiment for many months — this milestone achieved shows that the collider is heading back to full operations, which should get started again next year. There will be press conference about this on Monday November 23rd at 1:00 p.m. GMT, which will be webcast live.

And if you’re wondering what the crew at CERN think of this latest news, then take a look at this picture of them looking at the results of the start up:

In the full segment, they talk about Brian’s book Why E=mc2, which was excellent. I’ll try to write a review of it as soon as I can. In the meantime, I do have to praise Colbert for his insight; as Brian points out he was correct in his ideas! I was cheering along with the segment. It still cracks me up that the smartest and most insightful commentary on TV is not from any of the "real" news stations, but from satirical shows like Colbert and The Daily Show. They have better science coverage than CNN, MSNBC and anyone else combined.